This question haunted me about one and a half years ago.
I posted my then-boyfriend that question, and he told me that it would always be the parents’ fault. The answer was far from satisfactory, and it showed an extreme lack of responsibility, but I did not care enough to pursue the matter.
Today, I still do not have an exact answer to the question. A child’s upbringing will definitely influence his/her behaviour, motivated by values instilled into him/her. But when do you say somebody “did not know any better”, and when do you say somebody “should have known better”?
I have met people who, at 20, blame their parents for their bad habits and poor behaviour. But I have also met people who, by the time they hit 20, take full responsibility of their actions and refuse to attribute values and behaviour – whether good or bad – to upbringing, because they know better, and they know that they get to choose what kind of person they want to be.
Perhaps it could have something to do with locus of control. Perhaps it could be neurobiological. Perhaps it’s a person’s maturity level and emotional intelligence. Most likely, it’s all of these (and very likely more).
I’d like to hear as many thoughts on the matter as I can, so I suppose posting this here would be a good start.